首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Scientists studying the activity of the living brain with widely used new imaging techniques have been missing some of the earli
Scientists studying the activity of the living brain with widely used new imaging techniques have been missing some of the earli
admin
2012-07-13
63
问题
Scientists studying the activity of the living brain with widely used new imaging techniques have been missing some of the earliest steps in brain activity because those changes are subtle and are masked by reactions that happen seconds later, Israeli scientists say.
The imaging techniques — positron emission tomography scanning and magnetic resonance imaging, known as PET and functional M. R. I. scans — are used prominently in studies of brain activity. The most active brain areas appear to light up on the scans as specific tasks are performed. The two techniques do not measure nerve-cell activity directly; they measure the extra flow of blood that surges to the most active brain areas.
Researchers at the Weizmann Institute of Science in Rehovot, Israel, have monitored these changes in blood flow in anesthetized cats by removing parts of the skull and observing how the nerve cells in activated regions fuel their activities by rapidly removing oxygen from nearby red blood cells.
This rapid uptake of oxygen, made evident by visible changes in the color of the red cells, proves that early oxygen transfer gives these neurons the energy to do their work, the researchers said.
They also found that subtle changes in blood flow began significantly earlier than was detected by PET and functional M. R. I. scans, which lack sufficient
resolution
and do not form their images quickly enough to follow such rapid changes. Dr. Amiram Grinvald published the findings in the Journal Science.
"The initial event is very localized and will be missed if you don’t look for it soon enough and use the highest possible resolution," Dr. Grinvald said. " Now people are beginning to use our results with other imaging methods. "
Working on the exposed brain lets researchers follow electrical activity and the accompanying blood flow in greater detail than is possible by using indirect imaging methods that track neural activity through the skull. However, opportunities for open-skull studies of humans are limited to some kinds of neurosurgery, and researchers must mostly rely on PET and functional M. R. I. images for studies linking behavior with specific brain activity.
By directly observing exposed cat brains and in similar work with a few human cases, Dr. Grinvald and his associates have been able to observe the first evidence of electrical activity and other changes in brain cells after a light has been seen or a limb moved.
The newest research showed that it took three seconds or more after an event for the flow of blood to increase to an area of the brain dealing with a stimulus. That is the blood-flow increase usually pictured in brain-function studies with PET or functional M. R. I techniques, the Israeli researchers said. However, the initial reaction observed in the Weizmann research by directly imaging the exposed brain — the direct transfer of oxygen from blood cells to neurons — occurred in the first-tenth of a second and was lost to conventional imaging, they said.
The later increase in blood flow to the area, Dr. Grinvald said, was obviously an attempt by the body to supply more oxygen for brain activity. But the increase in blood was so abundant that it covered an area much larger than the region directly involved in the activity being studied, masking some of the subtle changes, he said.
The body’s reaction, the researchers said in the paper, was like "watering the entire garden for the sake of one thirsty flower. "
Dr. Kamil Ugurbil, said that the Israeli research provided clues that allowed the use of functional M. R. I. scans to picture earlier events in the activity of brain cells.
"Dr. Grinvald’s observations are very important, and they have significant implications for functional imaging with high resolution," Dr. Ugurbil said in an interview. " We have actually been able to look at the early changes with magnetic resonance imaging, but you need to use higher magnetic fields to see them clearly because they are small effects. "
By timing their images more carefully and by using stronger magnetic fields than normal, he said, researchers have used Dr. Grinvald’s findings to study early neuronal responses to stimuli at smaller, more specific sites in the brain.
The research done by Israeli researchers shows that the initial reaction — the direct transfer of oxygen from blood cells to neurons —______.
选项
A、occurred in the tenth of a second
B、occurred after the first-tenth of a second
C、could not be observed by conventional imaging
D、could be observed by conventional imaging
答案
C
解析
细节题型见第九段最后一句:然而,在Weizmann研究中通过对暴露的大脑直接成像所观察到的初始反应——直接将氧从血液细胞中输送到神经细胞中——发生在最初的十分之一秒,而这是常规成像会错过的。因此C为答案。
转载请注明原文地址:https://kaotiyun.com/show/MRgO777K
本试题收录于:
CATTI二级笔译综合能力题库翻译专业资格(CATTI)分类
0
CATTI二级笔译综合能力
翻译专业资格(CATTI)
相关试题推荐
ThedeathofDiana,PrincessofWales,onAug.31,1997,shookBritainandtheworld.TheNewYorkTimesaskedjournalistswhoc
HundredscamefromalloverThailandtogetoneofthefirstpublicglimpsesoftheWildBoars,thesmall-townyouthsoccerteam
Manyofthescientistsandengineersarejudged______howgreattheirachievementsare.
Thesimpleactofsurrenderingatelephonenumbertoastoreclerkmaynotseemharmful—somuchsothatmanyconsumersdoitwi
Ifpolicearecarryingarmsasamatterofcoursethendoesn’titencouragecriminalstocarrythem?
TheevidencethatsuchrepressiontookplaceinthewritingofAmericanhistoryisabundantlyprovidingbyAmericanliterature.
Thehousehelivedinfortenyearscollapsedyesterdaybecausesomeofthewoodhaddecayed.
Anyonewhois_________withtheseworkswillimmediatelyrecognizeinthepoemcertainreferencestovegetationceremonies.
Theoldwomangrewveryangrywhensherealizedhowshehadbeen_________outofhermoney.
AWesternintelligenceagencyestimatesbetween20to30peoplehavediedinthepowerstrugglebetweenmilitarygroupsandthe
随机试题
从诗歌的体裁上看,杜甫的《蜀相》是一首()
患者,女性,46岁。风心病,二尖瓣狭窄10余年,近1周来出现劳累后胸闷、心悸,休息后稍缓解,近2日来稍有体力活动即感呼吸困难,伴咳嗽、咳痰,昨日夜间睡眠中忽然因胸闷憋醒,今晨急诊入院。查体:P68次/分,HR98次/分,BP105/75mmHg,R
肱骨干中1/3骨折移位应是:
属于软土地基的工程特性的是()。
春秋战国时期是由原始社会向奴隶社会过渡的时期。()
简述符号学习、概念学习和命题学习的含义。
为保持水土、美化环境,H市准备在建设大道两侧栽一些樟树,要求路两侧树的棵数和间距均相等,且首、尾两端均栽上树。现在园林局已备好一批树苗,若每间隔3米栽一棵,则缺少18棵;若每间隔3.5米栽一棵,则缺少10棵。则要想使备用的树苗刚好够用,应该每间隔(
A、225B、22lC、114D、30B带有中心数字的圆圈形式数字推理,其规律为四周四个数字运算得到中间数字。两个圆圈中的数字均为合数,可能涉及乘法运算。第二个圆圈中,36是一个完全平方数,等于6×6,周围是4个3,可以确定是(3+3)×(3+3)
A、Theywererated8.3%higherthantheaverageones.B、Theyweresoldatanaveragepriceof$61perpair.C、Theywererated8.1
Onedayapoliceofficermanagedtogetsomefreshmushrooms.Hewassopleased【C1】______whathehadboughtthathe【C2】______
最新回复
(
0
)